A linear actuator (driving apparatus) using an electromechanical transducer element, such as a piezoelectric element, an electrostrictor element, or a magnetostrictor element, has heretofore been used as an actuator for auto-focusing or an actuator for zooming.
JP-B 3218851 (Patent Document 1) discloses a driving method of a driving apparatus using an electromechanical transducer element such as a piezoelectric element that is capable of suppressing ringing vibration generated in the electromechanical transducer element and of high-speed actuation. The driving apparatus disclosed in Patent Document 1 has the electromechanical transducer element such as the piezoelectric element, a driving member (vibration axis) bonded to the transducer element so that the driving member moves along with the transducer element, and a driven member (zoom lens body tube) friction-bonded to the driving member. In Patent Document 1, the driven member (zoom lens body tube) is driven with a devised driving signal being applied to the piezoelectric element (electromechanical transducer element).
Furthermore, JP-A 2006-304529 (Patent Document 2) discloses a high-performance driving apparatus using a movable element having a high bending modulus without lowering a moving speed or a driving force. The cost and weight of the driving apparatus can be reduced as compared to a case where the movable element is made of a metal material. The movable element of the driving apparatus disclosed in Patent Document 2 is formed of a liquid crystal polymer including carbon fiber. The driving apparatus disclosed in Patent Document 2 comprises a piezoelectric element (electromechanical transducer element) capable of expansion and contraction in response to an applied voltage, a driving axis (vibration friction portion) fixed to an end of the piezoelectric element in a direction of expansion and contraction of the piezoelectric element, a movable element (movement member) friction-bonded to the driving axis so as to be slidable with respect to the actuation axis, and a weight (stationary member or anchor) fixed to the other end of the piezoelectric element in the direction of expansion and contraction of the piezoelectric element by an adhesive. The driving axis is vibrated by varying the speed or acceleration of expansion and contraction of the piezoelectric element, so that the movable element (movement member) is moved along the driving axis (vibration friction portion).
Moreover, JP-B 3141714 (Patent Document 3) discloses a driving apparatus capable of stably actuating a movement member at a high speed. The driving apparatus disclosed in Patent Document 3 comprises a stationary member, an electromechanical transducer element fixed to an end of the stationary member in a direction of expansion and contraction of the electromechanical transducer element, a driving member (vibration friction portion) which is bonded to the other end of the electromechanical transducer element in the direction of expansion and contraction of the electromechanical transducer element and which is supported so as to be movable along the direction of expansion and contraction of the electromechanical transducer element, the movement member friction-bonded to the driving member and supported so as to be movable along the direction of expansion and contraction of the electromechanical transducer element, and frictional force providing means for generating a frictional force between the driving member (vibration friction portion) and the movement member. The frictional force adding means includes an elastic member fixed to the movement member for generating a pressing force and an insertion member for transmitting the pressing force generated by the elastic member to the driving member. A contacting portion between the movement member and the driving member and a contacting portion of the insertion member have a V-shaped cross-section.
JP-A 2002-119074 (Patent Document 4) discloses a driving apparatus using an electromechanical transducer element. The driving apparatus disclosed in Patent Document 4 comprises the electromechanical transducer element having an end fixed to a support base (stationary member), a vibration member (vibration friction portion) fixed to the other end of the electromechanical transducer element, and a movement body (movement member) engaging with the vibration member under a predetermined frictional force. A carbon rod is used as the vibration member (vibration friction portion).
Furthermore, JP-A 2006-141133 (Patent Document 5) discloses a driving apparatus having a short overall length. The driving apparatus disclosed in Patent Document 5 comprises an electromechanical transducer element having an end fixed to a fixed body (anchor or stationary member), a driving friction member (vibration friction portion) fixed to the other end of the electromechanical transducer element, and a movement body (movement member) friction-engaging with the driving friction member. Ceramic material, engineering plastic such as polyphenylene sulfide resin (PPS resin) or liquid crystal polymer (LCP resin), carbon fiber reinforced resin, and fiber-glass reinforced resin are used as a material for the driving friction member.
JP-A 2006-303955 (Patent Document 6) discloses an image pickup device capable of simplifying a structure and reducing cost. The image pickup device disclosed in Patent Document 6 comprises a lens driving part for moving an image pickup lens along an optical axis. The lens driving part employs SIDM (Smooth Impact Drive Mechanism). The lens driving partcomprises an SIDM weight portion attached to a driving-part attachment portion by a certain adhesive, a piezoelectric element portion (electromechanical transducer element) connected to the SIDM weight portion so as to be capable of expansion and contraction in a direction of an optical axis by energization, and a shaft portion (vibration friction portion) connected to the piezoelectric element portion so as to extend along the optical axis. The shaft portion of the lens driving part is sandwiched in a driving-part holding member (movement member) of a driving force transmission part along a direction substantially perpendicular to the optical axis.
JP-A 2007-202377 (Patent Document 7) discloses an electromechanical actuator structure capable of increasing a moving speed of a passive member and lowering an operating frequency of driving pulses. The electromechanical actuator structure disclosed in Patent Document 7 comprises an electric actuator (electromechanical transducer element) having a bottom joined to a base and a top surface, and an elastic driving member (vibration friction portion) joined to the top surface of the electric actuator. The elastic driving member comprises a stationary part joined to the top surface of the electric actuator so as to be reciprocated along with the electric actuator and an elastic part extending from the stationary part to the outside of the electric actuator and having a conductive part. A passive member (movement member) is provided within the conductive part of the elastic part of the elastic driving member. An elastic member is attached to the elastic part of the elastic driving member. The elastic member presses the passive member against the conductive part of the elastic part of the elastic driving member so that the passive member friction-engages with the conductive part of the elastic part of the elastic actuation member. Thus, the passive member (movement member) is moved along with the elastic driving member (vibration friction portion).